UiPath Extension Mozilla Firefox Error on Open Browser


I am new to this Forum and I am currently developing something on a VM on which I don’t have admin rights.

Now to my Issue:

I fetch data from the web and store the link in a DataTable to use it later.
If a certain condition matches the stored Website should open in Firefox.
But If it tries to open the site I get the following Error:

  • I checked the extension. Deactivated & Activated it.
  • In IE the site opens - but I can’t use IE.
  • I fetch the data from an open Firefox Browser so the extension should be fine.
  • I work on “Studio 2017.1.6.522 Enterprise Edition”
  • I added the site to trusted Websites.


I tested the “Open Browser” with the same site locally and it works fine.
So I guess the VM has some different configs which I can not change.
Thank you,

Hi @MaurerDa
If you setup Firefox extension again does it fix the error?

thanks for responding, but the issue stays the same:

"Main has thrown an exception

Source: Open browser

Message: Cannot communicate with the browser, please check the UiPath extension.

Exception Type: BrowserOperationException

UiPath.Core.BrowserOperationException: Cannot communicate with the browser, please check the UiPath extension. —> System.Runtime.InteropServices.COMException: Cannot communicate with the browser, please check the UiPath extension.
at UiPath.UiBrowserClass.Open(String bstrURL, UiBrowserFlags flag)
at UiPath.Core.Browser.Open(String url, Boolean privateSession, Boolean headlessSession, Boolean defaultSession)
— End of inner exception stack trace —
at UiPath.Core.Activities.ScopeActivity.EndExecute(NativeActivityContext context, IAsyncResult result)
at UiPath.Core.Activities.AsyncNativeActivity.BookmarkResumptionCallback(NativeActivityContext context, Bookmark bookmark, Object value)
at System.Activities.Runtime.BookmarkCallbackWrapper.Invoke(NativeActivityContext context, Bookmark bookmark, Object value)
at System.Activities.Runtime.BookmarkWorkItem.Execute(ActivityExecutor executor, BookmarkManager bookmarkManager)"

Let’s check together some steps. With Firefox browser open, run UiPath.DiagTool.exe from a console (same folder as UiStudio.exe) and verify that ChromeNativeMessaging.exe is running; You may find this line:


Name: ChromeNativeMessaging.exe
Path: … \UiPath\BrowserExtension\ChromeNativeMessaging.exe
Arguments: … \AppData\Local\UiPath\uipath-ff.json extension4ff@uipath.com

If this is not found, navigate to AppData\Local\UiPath\uipath-ff.json and check “path” value, it should point to a valid location where ChromeNativeMessaging.exe is located.

Finally, there should be a valid registry pointing to uipath-ff.json at Computer\HKEY_CURRENT_USER\Software\Mozilla\NativeMessagingHosts\com.uipath.chromenativemsg

This info is also explained here https://studio.uipath.com/docs/firefox-extension

I tried to run UiPath.DiagTool.exe but it crashed:

Next i checked the path and location of “ChromeNativeMessaging,exe” and it matches.

And lastly the registry point is valid.

Any more guesses?

Please collect low level logs of running the workflow and send me a private message with the .etl file